Hand riveter

ABSTRACT

A hand riverter is disclosed having a body with a fixed handle, and a movable handle mounted to lift a jaw case which houses the jaws, a jaw pusher, and a spring. The movable handle is composed of a first movable handle having a rolling member at its one end and a separate second movable handle having a curved cam surface substantially in elastic contact with the rolling member. The first and second movable handles are pivoted individually to constitute a double lever mechanism to assure smooth and reliable riveting operation with a small force. The jaw pusher includes spring rods engaged in the jaws to permit them to move away from and toward each other in elastic contact with the inner peripheral surface of a tapered bored end of the jaw case while maintaining their chucking surfaces in parallel to assure proper chucking action.

Miyamoto 1 June 3, 1975 1 HAND RIVETER Primary Examiner-Milton S. Mehr[75] Inventor. Uklo Mlyamoto, Osaka, Japan Assismm Examiner Gene P.Crosby Assigneei Vessel Tool mp y. d" aka. Allorney, Agent, orFirmArmstrong, Nikaido &

Japan Wegner [22] Filed: July 8, 1974 [2]] Appl. No.: 486,426 l57lABSTRACT A hand riverter is disclosed having a body with a fixed handle,and a movable handle mounted to lift a jaw [30] Fomgn ApplicationPriority Dam case which houses the jaws, a jaw pusher. and a July l9.1973 Japan 48-85202 p g The movable handle is composed of a firstmovable handle having a rolling member at its one [52] US. Cl. 72/391and and a separate Second movable handle having a [51] I'll. Cl B21]15/3? curved cam Surface substantially in elastic Contact Fleld OfSearch 114, 453, the rolling member. The first and second 29/24135324354 able handles are pivoted individually to constitute a double levermechanism to assure smooth and reliable [56] References cued rivetingoperation with a small force. The jaw pusher UNITED STATE PATENTSincludes spring rods engaged in the jaws to permit 3,082,898 3/1963Bosch 72/391 them to move away from and toward each other in 3,100.5788/1963 Halverson........... 72/39l elastic contact with the innerperipheral surface of a $324,700 6/l967 Eliiott 72/39l tapered bgred endof the jaw case while maintaining 3,49l,578 l/l970 Biermann 72/39l theirchucking Surfaces in paranel to assure proper 3,561,249 2/197] Freemann72/391 chucking action 3,646.800 3/l972 Martin 72/391 3,782,l65 l/l974BOSCh 72/391 2 Claims 7 Drawing Figures 3,83l,424 8/[974 .lames 72/39l18 29 21 A) 19 a a l j 13 14 9 Ln .r 12 2' V 8 1: l t' k. v/ J 2 f I 1 72 2 B i I 25 :5 l 26 l s I 29 J 24 17 PATENTEU Jun 3 ms SHEET 1 Mammy-:31975 3.865; 782

SHEET HAND RIVETER BACKGROUi D OF THE INVENTION The present inventionrelates to improvements in riveters for fastening plate-like memberstogether with rivets composed of a rivet tube having a flange at one endand a nail-like mandrel serving as a core of the rivet and inserted intothe rivet tube from the other end thereof. with the head of the mandrelsupported by the other end of the rivet tube. More particularly. theinvention relates to improvements in hand riveters for conductingriveting operation with rivets of the type described.

Riveters have already been known by which platelike members are joinedtogether with the abovementioned rivets as disclosed in Japanese UtilityModel Publications Nos. 23.918/1970; l8.957/l97l; 18,958/l97l and18.959/1971. US. Pat. Nos. 3.082,898 and 3.IOO,578. These riveters aredivided into two types: hand riveters for manual riveting operation andpower-operated riveters employing air, oil or like pressure medium apower source for riveting operation.

With riveters of either type, a plurality of members are fastenedtogether by passing a flanged rivet tube through the members, insertinga headed mandrel into the rivet tube, subjecting one end of the rivettube to plastic deformation to diametrically expand the end with thehead of the mandrel by drawing the mandrel in an axial direction andsnapping off the mandrel at its neck portion to leave the head in theexpanded deformed end as a core so that the members will be heldtogether by the flanged end and the deformed end of the rivet tube.

To perform the operation described above, the riveter generally includesdivided jaws which are adapted to chuck the mandrel and spring-loaded toelastically engage in the tapered bore of a jaw case. Further to renderthe riveter serviceable for versatile uses, a plurality of nosepiecesare prepared for the riveter in conformity with various sizes of rivetassemblies. The nosepiece is detachably mounted in the rivet and, whenset in position. the nosepiece pushes the jaws open so that the mandrelcan be chucked by the jaws.

When the jaws are brought to position for chucking the mandrel, amovable handle is pushed toward a fixed handle by grasping if theriveter is of the manual type. thereby pulling the mandrel in the axialdirection while the mandrel is being chucked firmly by the jaws. If theriveter is power-operable, the same operation is effected withcompressed air or pressure medium which substitutes the manipulation ofhandle. The poweroperated riveter is advantageous in that the air orpressure medium serving as the power source is very effective in drawingthe mandrel in the axial direction, but it is inferior in portablility,complex in overall construction and very costly. Moreover. it has thedrawback that when in condition for chucking the mandrel, the slightestdisplacement of the chucking element would affect adversely on thesubsequent operation of drawing the mandrel in the axial direction.

Such drawback has been experienced with the power-operatcd riveterdisclosed in US. Pat. No. 3,082,898 which is the typical of its kind.With the riveter disclosed. the action of a jaw spring is deliveredthrough ajaw pusher tojaws. which are in turn engaged elastically intothe tapered bore of a jaw case. the jaws being adapted to be pushedapart by the inner end of a nozzle screwed in to receive the mandrel forchucking action. If in this case the nozzle and the jaws are notuniformly smooth-surfaced for contact with each other and the contactsurfaces of the jaw pusher and jaws lack uniform smoothness. forexample. due to abrasion caused by years of service, the opposingdivided jaws will be pushed open in uneven fashion. with the result thatthe mandrel will not longer be chucked properly. According to US. Pat.No. 3.100.578. the nozzle is not designed to push open the jaws and.accordingly. there will be no objectionable contact between the nozzleand the jaws which would displace one jaw from the other. However, ifthe chucking surfaces of the jaws should involve an uneven portion, themandrel will not be chucked properly as in the above-mentioned case.Likewise. the riveters disclosed in Japanese Utility Model PublicationsNo. 23.9]8/1970, No. 18,957/1971, etc.. have the same drawback. Suchdrawback is attributable to the construction in which the divided jawsare simply pressed on by the jaw spring via the jaw pusher. With theseknown riveters, it is difficult to correct displacement or improperchucking action once such objection occurs and irregular break ofmandrel or damage to the jaws therefore results.

Thus, despite its usefulness, the riveter of the poweroperated type hasfound only limited applications because of the foregoing disadvantagesinvolving poor economy. In fact, many of the riveters presently used areof the manual type.

As compared with the power-operated riveter, the hand riveter which ismanually operable is inferior with respect to its ability to draw themandrel axially in gripping engagement therewith. but it is easy tohandle and inexpensive and will become more useful than thepower-operated riveter, if it has a greater ability to draw the mandreland that in parallel to the axial direction. For example, JapaneseUtility Model Publication No. l8,957/l 97l discloses a hand riveterincluding a sector gear provided at the end of a movable handle andmeshing with a lever-like sector gear mounted on the jaw case so as toimpart a greater ability to the movable handle. However, theconstruction fails to assure accurate and reliable meshing engagementbetween the sector gears, which are therefore liable to damage.Moreover. the riveter lacks smoothness in its operation and is expensiveto make. Furthermore according to US. Pat. No. 3,100,578, the movablehandle is formed at its end with a cam surface which proves useful inimprov ing the smoothness of operation. However, the riveter has notbeen improved sufficiently in exhibiting a great ability to draw themandrel in the axial direction, since the lever mechanism merely employsa single lever.

SUMMARY OF THE INVENTION An object of this invention is to overcome theproblems and drawbacks of conventional riveters described above and toprovide a hand riveter which is simple. smoothly operable, durable,efficient and relatively inexpensive.

Another object of this invention is to provide a hand riveter havingmovable handle means incorporating therein a double lever mechanism tomake it sure that riveting operation will be conducted with a smallforce.

Another object of this invention is to provide a hand riveterincorporating therein the above-mentioned double lever mechanismcomprising a first movable handle and a second movable handle formed, ata portion thereof where it applies a force to the first handle, with acam surface so shaped as to permit a small constant force to effectriveting operation smoothly all the time.

Still another object of this invention is to provide a hand riveterwherein divided jaws can be so positioned as to chuck the mandreluniformly all the time regardless of the type of mandrel, such that evenif the jaws are brought out of position the chucking surfaces of thejaws will come into face-to-face contact with the mandrel when chuckingthe same, the hand riveter thus having a high ability to chuck themandrel.

The foregoing object of this invention to impart a great ability to thehand riveter and to render the same operable smoothly can be achieved bythe construction of this invention in which the above-mentioned movablehandle means comprises separate first movable handle and second movablehandle to provide a double lever mechanism, the movable handle meansincluding a cam surface of a special shape in combination with a rollingmember in contact with the cam surface.

The hand riveter of this invention comprises a fixed handle having ahollow body at its head portion; a jaw case housed in the hollow body inaxially movable manner and accommodating jaws, a jaw pusher and a jawspring, the jaw spring acting on the jaws by way of the jaw pusher toelastically bring the jaws into contact with the inner peripheralsurface of a tapered bore at one end of the jaw case; movable handlemeans opposing the fixed handle and mounted on the jaw case; a springinterposed between the fixed handle and the movable handle means toelastically bring the bored end of the jaw case into contact with thebottom of the hollow body; and a nosepiece having a flange and a piecingbore for passing a mandrel serving as a core of a rivet, the nosepiecebeing mountable from outside into the hollow body through the bottomthereof with the flange abutting against the bottom so as to cause theinner end of the nosepiece to act on the jaws and to thereby push thejaws outward away from each other. The movable handle means comprises afirst movable handle carrying a rolling member at its one end and asecond movable handle having a cam surface at its base portion, theseparate first and second movable handles constituting a double levermachanism. The first movable handle is mounted, at the other endthereof, on the upper portion ofthe jaw case and is pivoted to the headportion at an intermediate portion thereof that is as close as possibleto the mounted position. The first handle extends rearward andterminates at the end where it carries the rolling member.

The second movable handle is in the form of a bell crank and is pivotedat its front end to the head portion. The cam surface at the baseportion of the second handle opposes the rolling member. By virtue ofspring action, the rolling member substantially bears against the camsurface elastically. The free end of the second movable handle extendsrearward in opposing relation to the fixed handle, the extension beingpositioned substantially at an angle to the fixed handle. Accordingly,the second movable handle is spaced apart from the fixed handle by aprogressively increasing distance toward the free end. When the free endof the second movable handle is moved toward the fixed handle, the firstmovable handle carrying the rolling member elastically in contact withthe cam surface turns about its pivot, forcing the jaw case upward inthe hollow body,

whereby the divided jaws which have been elastically engaged in thetapered bore of the jaw case draw the mandrel in the axial direction infirm chucking engage- 5 ment therewith.

The double lever mechanism comprising the first and second movablehandles exhibits a great ability to draw the mandrel in the axialdirection with a very small force applied on the second movable handle.To allow the double lever mechanism to operate smoothly and to eliminatethe power loss in the lever mechanism. the cam surface is curvedprogressively gently rearward and the rolling contact of the rollingmember with the cam surface renders the mechanism operable with improvedsmoothness. The progressively gently curving cam surface serves tominimize the distance between the pivot of the second movable handle andthe position where the contact between the cam surface and rollingmember takes place, this preventing the loss of operating force.

To make it sure that the mandrel will be chucked reliably, the jaws canbe pushed apart by the nosepiece while the opposing chucking surfacesare being maintained in parallel relation. in this respect, the jawpusher is made serviceable not only to deliver the action of the jawspring to the jaws but also to permit the chucking surfaces to be pushedapart while being maintained in parallel relation to each other. Morespecifically, the jaw pusher interposed between the jaw spring and thejaws has the following construction. Spring rods equal in number to thenumber of the divided jaws and extending axially of the jaw case arefixed, each at its one end, to the jaw pusher serving as a seat for thespring, the free ends of the spring rods being progressively directedslightly outward. The free ends of the spring rods are engaged in thetop surfaces of the jaws loosely, such that the spring rods and jaws aremovable upward and downward relative to each other, the jaws beingturnable with respect to the spring rods.

Accordingly, when the jaws are to be placed into the tapered bore of thejaw case, the spring rods are loosely fitted into the jaws respectively,with the distance between the opposing spring rods reduced to positionthe rods substantially in parallel to each other and to thereby bias thejaws outward away from each other all the time. Thus when the jaws areopened to the chucking position by the inner end of the nosepiecemounted from outside into the bottom of the hollow body, the jaws aresubjected to the action of the spring rods which tends to force the jawsoutward. Inasmuch as the spring rods are generally in parallel, the jawswill be pushed apart outward. with their chucking surfaces kept inparallel for face-to-face contact with the mandrel to be chucked.

Even if the jaws are displaced from each other and are not positionedproperly for chucking action before the nosepiece is mounted. the jaws,being turnable relative to the spring rods, can be brought to correctposition by the nosepiece when the nosepiece is set in place.

These and other objects, features and advantages of this invention willbecome more apparent from the following description with reference tothe accompanying drawings showing an embodiment of the invention forillustrative purposes only.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a front view showing anembodiment of the riveter of this invention in its entirety;

FIG. 2 is a view partly in section showing the same and alsoillustrating the steps of operating a movable handle;

FIG. 3 is a perspective view showing a mandrel chucking assembly asexploded;

FIG. 4 is a view partly broken away and showing an example of rivetassembly to be used according to this invention;

FIG. 5 is a fragmentary enlarged view in section illustrating rivetingoperation, the mandrel chucking assembly being shown as it is ready foroperation;

FIG. 6 is a similar view showing the mandrel chucking assembly duringriveting operation; and

FIG. 7 is a similar view showing the same upon completion of rivetingoperation.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIGS. 1 and 2,a fixed handle 1 has a hollow body 2 at its head portion. The hollowbody 2, positioned generally at right angles to the fixed handle 1, hasat its lower end threaded grooves 3 and 3 defining a bore foraccommodating a nosepiece. The head portion adjacent the hollow body 2is composed of side walls 4 and 4 opposing each other in parallel.Disposed in the hollow body 2 is a cylindrical jaw case 5 which ismovable axially of the body 2. The inner peripheral wall of the jaw case5 at is lower end is tapered to provided a bore 6. As seen in FIG. 3,the jaw case 5 includes at its upper end a forked portion 8 having pivotholes 7.

For the axial displacement of the jaw case 5. the fixed handle 1 isprovided with movable handle means serving as a double lever mechanismand comprising separate first movable handle 9 and second movable handle10. The first movable handle 9 is in the form of a flat plate andcarries at its one end a rollable rolling member 11 made of a super-hardmetal material and disposed transversely thereof.

The second movable handle is approximately in the form of a bell crankand has a cam surface 12 at a bent base portion. The cam surface 12 iscurved gently progressively rearward.

The first movable handle 9 is pivotally mounted, at its front end, inthe forked portion 8 of the jaw case 5 by means ofa pivot 13 inserted inthe pivot holes 7. Another pivot 14 supported by the opposite side walls4 and 4 extends through the first movable handle 9, the pivot 14 beingpositioned as close as possible to the pivot 13.

A spring 16 wound around a pin 17 is disposed between the first movablehandle 9 and the fixed handle I, more specifically between the firstmovable handle 9 and the bottom wall of the head portion. The spring l6acts elastically on the first movable handle 9 all the time. so that thefirst movable handle 9, fulcrumed by the pivot l4. presses the jaw case5 into contact with the bottom of the hollow body 2 elastically.

at l6. the rolling member II is substantially held in elastic contactwith the cam surface 12. From the position of the cam surface 12, thesecond movable handle 10 extends further rearward, the extensionopposing the fixed handle 1 and being spaced apart therefrom by aprogressively increasing distance rearward. Thus the second movablehandle 10 extends in slanting fashion.

When the free end of the second movable handle 10 is grasped and pushedtoward the direction of arrow A in FIG. 2 against the action of thespring 16. the rolling member 11 rolls on the cam surface 12 smoothly.permitting the first movable handle 9 to be depressed in the directionof arrow B in FIG. 2 about the pivot l4. In this way. the double levermechanism can lift the jaw case 5 with a very small force. Inasmuch asthe first movable handle 9 is pivoted at the position as close aspossible to the pivot 13 connecting the handle 9 to the jaw case 5, themechanism works very effectively and makes it possible to force up thejaw case 5 approximately in linear fashion.

When the jaw case 5 is shifted upward as required to snap off themandrel as will be described later, the first movable handle 9 almostcomes into contact with the bottom wall 15. The bottom wall 15 thereforeserves as a stopper by contact with the handle 9. As already apparentfrom the description above, the position of contact between the rollingmember II and the cam surface 12 will become progressively remote fromthe pivot 18 of the second movable handle 10 as the operation proceeds.resulting in a loss of the applied force, but the cam surface 12 whichis curved progressively gently serves to minimize the loss of the force.Despite the power loss involved, the present mechanism achieves anoutstanding lever action as compared with conventional single levermechanism. The curved cam surface 12 enables the rolling member 11 toroll along with improved smoothness.

To prevent shake of the first and second movable handles 9 and 10 asthey turn about their fulcrums between the opposite side walls 4 and 4,guide pins 19 and 20 project from the side surfaces of the handles 9 and10, respectively, in contact with the inner surfaces of the side walls 4and 4. Further to limit the reverse turning of the second movable handle10, a stopper pin 2] extends between the side walls 4 and 4 at an upperposition close to the base end of the handle 10.

An assembly is housed in the jaw case 5 to chuck the mandrel during theoperation stated above. The components of the chucking assembly areshown in FIG. 3. The chucking assembly comprises divided jaws 24 adaptedto chuck the mandrel and having chucking surfaces 22 in opposingrelation and tapered peripheral surfaces 23 at their lower endsrespectively, a jaw spring 25 for bringing the tapered surfaces 23 intoelastic contact with the inner peripheral wall of the tapered bore 6 ofthe jaw case 5, ajaw pusher 26 interposed between the jaws 24 and thespring 25 to deliver the action of the spring 25 to the jaws 24, aretaining nut 27 for adjusting the elastic action of the jaw spring 25,and the aforementioned jaw case 5.

The jaw pusher 26 not only serves to deliver the elastic force of thespring 25 to the jaws 24 but also permits the jaws 24 and 24 to moveaway from and toward each other with the chucking surfaces 22 and 22maintained in parallel all the time.

To this end. slender spring rods 29 equal in number to the number of thejaws 24 and circular in cross section are partially embedded in andspot-welded to the under surface of the jaw pusher 26 serving as aspring seat, the spring rods 29 being made of an elastic material suchas metal. Before the spring rods 29 are placed into the assembly, therods extend outward toward their lower ends as seen in FIG. 3. Each ofthe jaws 24 is formed in its top surface with a bore 30 having aslightly greater diameter than the spring rod 29 and extending axiallythereof.

To place the parts into the jaw case 5, the spring rods 29 and 29 areinserted into the bores 29 and 29 to bring the jaws 24 and the pusher 26together first, the jaws 24 are then placed into the jaw case S fromabove, the jaw spring 25 is thereafter inserted into the case 5, and theretaining nut 27 is finally screwed into the case 5. The action of thejaw spring 25 therefore acts through the jaw pusher 26 on the jaws 24and 24 to elastically fit the tapered surfaces 23 of the jaws 24 in thetapered bore 6. Consequently, the tips of the jaws 24 will be exposedslightly from the tapered bore 6 to position in the threaded bore 3 asshown in FIG. 2, with the result that the spring rods 29 and 29 arespaced apart by a reduced distance substantially in parallel to eachother, biasing the jaws 24 and 24 outward all the time. At this time,the divided surfaces 220 at the opposite sides of the chucking surfaces22 are in intimate contact with each other (see FIG. 3). Since thespring rods 29 and 29 are held generally in parallel to each other whilerendering the jaws 24 and 24 turnable relative to the spring rods 29 and29, the possible displacement of the intimately fitted divided surfaces220 can be corrected. Even when subjected to the action of the jawspring 25, the spring rods 29 will still remain in shape againstbuckling because they are positioned generally in parallel and are madeof metal.

A plurality of members 33 and 33 are joined together using a rivetassembly consisting ofa rivet tube 31 having a flange 310 at its one endand a nail-like mandrel 32 serving as a core of the rivet and having ahead 32a and a notch 32b formed proximate to the head 32a as shown inFIG. 4. Such rivets are available usually in about three sizes, so thatnosepieces 34 are prepared for use with rivets of various sizes and areusually detaehably mounted in the bottom wall as seen in FIGS. 1 and 2.

The nosepiece 34 has a center bore 34a for receiving the mandrel, anintermediate flange 34b and a jaw pushing portion 340 at its extremeupper end and is threaded in its upper peripheral wall. For use with alarger rivet, the mandrel receiving bore 340 will have a greaterdiameter, with an increased distance between the inner surface of theflange 34b and the upper or inner end of the pushing portion 340.

For a better understanding of this invention, riveting operation by thepresent hand riveter will be described below in sequential order withreference to FIGS. 5 to 7.

As in conventional manner, a rivet tube 31 is fitted into plate members33 and 33, and a nosepiece 34 in conformity therewith is screwed intothe bore 3 against the action of the jaw spring 25. When the nosepiece34 is thus set in position, the inner surface of the flange 34h bearsagainst the bottom of the hollow body 2, with the inner end of thepushing portion 34c abutting against the jaws 24 and 24 to separate thedivided jaws 24 and 24 to an extent suitable to chuck the particularmandrel 32.

When the jaws 24 and 24 are to be brought to the position for chuckingaction. they are subjected to the outward biasing action of the springrods 29 and 29 which are generally in parallel to each other, so thatthe jaws 24 and 24 are forced outward against the jaw spring 25 whiletheir chucking surfaces 22 and 22 are being maintained in parallel,Accordingly, the jaws 24 and 24 can be brought into face-to-face contactwith the mandrel 32 when chucking the mandrel by the subsequentmanipulation of the second movable handle I0. The mandrel receiving bore340 and a chucking bore now defined by the outwardly displaced chuckingsurface 22 and 22 are coaxial with each other. The mandrel 32 isinserted into the rivet tube 3I and the distal end of the mandrel ispassed through the nosepiece 34 and chucking bore.

Subsequently, the second movable handle I0 is grasped to lift the jawcase 5 axially of the hollow body 2, permitting the jaw spring 25 todepress the jaws 24 and 24 with its spring force. Since the taperedsurfaces 23 fit in the tapered bore 6 elastically, the jaws 24 and 24are brought closer toward each other with progressive descrease in thedistance between their chucking surfaces 22 and 22 and finally chuck themandrel 32. When chucking in this way, the jaws 24 and 24 are subjectedto the action of the spring rods 29 which tends to restore them to theparallel position, namely to bring them diametrically inward, while thejaws 24 and 24 are turnable with respect to the spring rods 29 and 29.Thus the jaws are brought to correct chucking position to achieveuniform face-to-face contact between the chucking surfaces 22, 22 andthe mandrel 32 and to thereby hold the mandrel firmly. The movablehandle 10 is now in position (I) in FIG. 2.

The second movable handle 10 is pushed further toward the fixed handle1, causing the head 32a of the mandrel 32 to progressively compress andcollapse the rivet tube 31 (see FIG. 6) while subjecting the mandrel 32to high tension in axial direction until the mandrel 32 is snapped offat the notched portion 32b. Consequently, the head 32a of the mandrel 32remains as a core in the portion 31 which has been expanded and deformedby compression, whereby the members 33 and 33 are completely fastenedtogether. At this time. the movable handle It) assumes position (II) inFIG. 2. In the case where the largest rivet is used, the first movablehandle 9 almost comes into contact with the bottom wall 15.

Since the movable handle means comprises the separate first and secondhandles 9 and 10 to provide a double lever mechanism, the presentriveter operates very effectively with a small force. When the riveteris freed from the operating force, the spring 16 acts to turn or movethe parts in opposite directions to the foregoing. rendering theapparatus ready for the next riveting operation.

As will be apparent from the description given above. the hand riveterof this invention is operable with a very small force and is thereforeeasy and convenient to handle. In addition. the chucking assemblyoperates reliably to hold the mandrel firmly, making it sure that aplurality of members can be riveted together with high reliability. Thusthe invention is of immense value for industrial uses.

What is claimed is:

l. A hand riveter comprising divided jaws, a jaw spring for elasticallypressing the jaws, a jaw pusher interposed between the jaws and the jawspring to deliver the elastic force of the jaw spring to the jaws, a jawcase housing the jaws, the jaw spring and the jaw pusher and having atapered bore for receiving the jaws in elastic contact wth the innerperipheral surface of the tapered bore, a fixed handle having at itshead portion a hollow body acommodating the jaw case therein movablyaxially thereof, a nosepiece mountable from outside into the hollow bodyto open the jaws away from each other and movable handle means mountedon the jaw case to lift the jaw case and opposing the fixed handle, themovable handle means being composed ofa first movable handle having arolling member at its one end and a separate second movable handle inthe form ofa bell crank and formed at its base portion with a camsurface curved progressively gently rearward, the rolling member beingsubstantially in elastic contact with the cam surface, the first andsecond movable handles being pivoted individually so as to serve as adouble lever mechanism.

2. A hand riveter comprising divided jaws, a jaw spring for elasticallypressing the jaws, a jaw pusher interposed between the jaws and the jawspring to deliver the elastic force of the jaw spring to the jaws, a jawcase housing the jaws, the jaw spring and the jaw pusher and having atapered bore for receiving the jaws in elastic contact with the innerperipheral surface of the tapered bore, a fixed handle having at itshead portion a hollow body accommodating the jaw case therein movablyaxially thereof, a nosepiece mountable from outside into the hollow bodyto open the jaws away from each other and movable handle means mountedon the jaw case to lift the jaw case and opposing the fixed handle, thejaw pusher including a spring seat and spring rods equal in number tothe number of the divided jaws and fixed to the spring seat each at itsone end, the spring rods extending downward from the spring seatprogressively outward but being positioned in parallel to each otherwhen the jaws are turnably mounted thereon within the jaw case, the jawsbeing movable away from and toward each other in elastic contact withthe inner pe ripheral surface of the tapered bore while maintainingtheir chucking surfaces in parallel to each other.

1. A hand riveter comprising divided jaws, a jaw spring for elasticallypressing the jaws, a jaw pusher interposed between the jaws and the jawspring to deliver the elastic force of the jaw spring to the jaws, a jawcase housing the jaws, the jaw spring and the jaw pusher and having atapered bore for receiving the jaws in elastic contact wth the innerperipheral surface of the tapered bore, a fixed handle having at itshead portion a hollow body acommodating the jaw case therein movablyaxially thereof, a nosepiece mountable from outside into the hollow bodyto open the jaws away from each other and movable handle means mountedon the jaw case to lift the jaw case and opposing the fixed handle, themovable handle means being composed of a first movable handle having arolling member at its one end and a separate second movable handle inthe form of a bell crank and formed at its base portion with a camsurface curved progressively gently rearward, the rolling member beingsubstantially in elastic contact with the cam surface, the first andsecond movable handles being pivoted individually so as to serve as adouble lever mechanism.
 1. A hand riveter comprising divided jaws, a jawspring for elastically pressing the jaws, a jaw pusher interposedbetween the jaws and the jaw spring to deliver the elastic force of thejaw spring to the jaws, a jaw case housing the jaws, the jaw spring andthe jaw pusher and having a tapered bore for receiving the jaws inelastic contact wth the inner peripheral surface of the tapered bore, afixed handle having at its head portion a hollow body acommodating thejaw case therein movably axially thereof, a nosepiece mountable fromoutside into the hollow body to open the jaws away from each other andmovable handle means mounted on the jaw case to lift the jaw case andopposing the fixed handle, the movable handle means being composed of afirst movable handle having a rolling member at its one end and aseparate second movable handle in the form of a bell crank and formed atits base portion with a cam surface curved progressively gentlyrearward, the rolling member being substantially in elastic contact withthe cam surface, the first and second movable handles being pivotedindividually so as to serve as a double lever mechanism.